U.S. patent application number 12/519844 was filed with the patent office on 2010-07-29 for photocatalytic coating.
Invention is credited to Mark T. Anderson, Feng Bai, Rachael A.T. Gould.
Application Number | 20100190633 12/519844 |
Document ID | / |
Family ID | 39562899 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100190633 |
Kind Code |
A1 |
Bai; Feng ; et al. |
July 29, 2010 |
PHOTOCATALYTIC COATING
Abstract
In one aspect, the present invention is directed to a coating
composition. The coating composition comprises a dispersion of
photocatalysts having a mean cluster size of less than about 300 nm
and an alkali metal silicate binder. In another aspect, the present
invention is directed to a coated article. The coated article has a
photocatalytic coating with improved transparency on its external
surface that is formed from the aforesaid coating composition.
Inventors: |
Bai; Feng; (Woodbury,
MN) ; Gould; Rachael A.T.; (Forest Lake, MN) ;
Anderson; Mark T.; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
39562899 |
Appl. No.: |
12/519844 |
Filed: |
December 17, 2007 |
PCT Filed: |
December 17, 2007 |
PCT NO: |
PCT/US07/87698 |
371 Date: |
March 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60871576 |
Dec 22, 2006 |
|
|
|
Current U.S.
Class: |
502/63 |
Current CPC
Class: |
C09D 7/67 20180101; C09D
7/68 20180101; B01J 37/0215 20130101; C04B 41/5089 20130101; B01J
35/004 20130101; E04D 13/002 20130101; C09D 7/61 20180101; Y02W
30/91 20150501; C04B 2111/00586 20130101; C09D 1/02 20130101; C04B
28/26 20130101; Y02W 30/94 20150501; E04D 7/005 20130101; C04B
2111/2061 20130101; C04B 20/1077 20130101; C08K 3/22 20130101; C04B
2111/00827 20130101; C04B 28/26 20130101; C04B 14/30 20130101; C04B
14/305 20130101; C04B 2103/54 20130101; C04B 41/5089 20130101; C04B
41/5041 20130101; C04B 20/1077 20130101; C04B 14/14 20130101; C04B
18/14 20130101 |
Class at
Publication: |
502/63 |
International
Class: |
B01J 21/06 20060101
B01J021/06; B01J 21/16 20060101 B01J021/16; B01J 23/04 20060101
B01J023/04 |
Claims
1. A coated article, comprising: an article having an external
surface and a coating on the external surface of the article,
wherein the coating is formed from a composition comprising a
dispersion of photocatalysts having a mean cluster size of less
than about 300 nm and an alkali metal silicate binder.
2. The coated article of claim 1, wherein the article is a roofing
granule.
3. The coated article of claim 1, wherein the article is a
tile.
4. The coated article of claim 1, wherein the photocatalysts
comprise TiO.sub.2, ZnO, WO.sub.3, SnO.sub.2, CaTiO.sub.3,
Fe.sub.2O.sub.3, MoO.sub.3, Nb.sub.2O.sub.5,
Ti.sub.xZr.sub.(1-x)O.sub.2, SiC, SrTiO.sub.3, CdS, GaP, InP, GaAs,
BaTiO.sub.3, KNbO.sub.3, Ta.sub.2O.sub.5, Bi.sub.2O.sub.3, NiO,
Cu.sub.2O, SiO.sub.2, MoS.sub.2, InPb, RuO.sub.2, CeO.sub.2,
Ti(OH).sub.4, or combinations thereof.
5. The coated article of claim 1, wherein the photocatalysts
comprise crystalline anatase TiO.sub.2, crystalline rutile
TiO.sub.2, crystalline ZnO, or combinations thereof.
6. The coated article of claim 1, wherein the photocatalysts are
doped with C, N, S, F, Pt, Pd, Au, Ag, Os, Rh, RuO.sub.2, Nb, Cu,
Sn, Ni, Fe, or combinations thereof.
7. The coated article of claim 1, wherein the alkali metal silicate
binder comprises lithium silicate, sodium silicate, potassium
silicate, or combinations thereof.
8. The coated article of claim 1, wherein the alkali metal silicate
binder comprises a pigment.
9. The coated article of claim 1, wherein each of the absolute
values of the difference in the L*, a*, b* numbers between the
coated article and the base article is less than about 2.
10. A coated roofing granule, comprising: a roofing granule having
an external surface and a coating on the external surface of the
roofing granule, wherein the coating is formed from a composition
comprising a dispersion of photocatalysts having a mean cluster
size of less than about 300 nm and an alkali metal silicate binder,
and wherein each of the absolute values of the difference in the
L*, a*, b* numbers between the coated granule and the base granule
is less than about 2.
11. A coating composition, comprising: a dispersion of
photocatalyts having a mean cluster size of less than about 300 nm
and an alkali metal silicate binder.
12. The coating composition of claim 11, wherein the photocatalysts
comprise TiO.sub.2, ZnO, WO.sub.3, SnO.sub.2, CaTiO.sub.3,
Fe.sub.2O.sub.3, MoO.sub.3, Nb.sub.2O.sub.5,
Ti.sub.xZr.sub.(1-x)O.sub.2, SiC, SrTiO.sub.3, CdS, GaP, InP, GaAs,
BaTiO.sub.3, KNbO.sub.3, Ta.sub.2O.sub.5, Bi.sub.2O.sub.3, NiO,
Cu.sub.2O, SiO.sub.2, MoS.sub.2, InPb, RuO.sub.2, CeO.sub.2,
Ti(OH).sub.4, or combinations thereof.
13. The coating composition of claim 11, wherein the photocatalysts
comprise crystalline anatase TiO.sub.2, crystalline rutile
TiO.sub.2, crystalline ZnO, or combinations thereof.
14. The coating composition of claim 11, wherein the photocatalysts
are doped with C, N, S, F, Pt, Pd, Au, Ag, Os, Rh, RuO.sub.2, Nb,
Cu, Sn, Ni, Fe, or combinations thereof.
15. The coating composition of claim 11, wherein the alkali metal
silicate binder comprises lithium silicate, sodium silicate,
potassium silicate, or combinations thereof.
16. The coating composition of claim 11, wherein the alkali metal
silicate binder comprises a pigment.
17. A method of making a coated article, comprising: providing an
article having an external surface, providing a composition
comprising a dispersion of photocatalysts having a mean cluster
size of less than about 300 nm and an alkali metal silicate binder,
depositing the composition onto the article, and heating the
deposited article to form a coating thereon.
18. The method of claim 17, wherein the article is a roofing
granule.
19. The method of claim 17, wherein the article is a tile.
20. The method of claim 17, wherein the photocatalysts comprise
TiO.sub.2, ZnO, WO.sub.3, SnO.sub.2, CaTiO.sub.3, Fe.sub.2O.sub.3,
MoO.sub.3, Nb.sub.2O.sub.5, Ti.sub.xZr.sub.(1-x)O.sub.2, SiC,
SrTiO.sub.3, CdS, GaP, InP, GaAs, BaTiO.sub.3, KNbO.sub.3,
Ta.sub.2O.sub.5, Bi.sub.2O.sub.3, NiO, Cu.sub.2O, SiO.sub.2,
MoS.sub.2, InPb, RuO.sub.2, CeO.sub.2, Ti(OH).sub.4, or
combinations thereof.
21. The method of claim 17, wherein the photocatalysts comprise
crystalline anatase TiO.sub.2, crystalline rutile TiO.sub.2,
crystalline ZnO, or combinations thereof.
22. The method of claim 17, wherein the photocatalysts are doped
with C, N, S, F, Pt, Pd, Au, Ag, Os, Rh, RuO.sub.2, Nb, Cu, Sn, Ni,
Fe, or combinations thereof.
23. The method of claim 17, wherein the alkali metal silicate
binder comprises lithium silicate, sodium silicate, potassium
silicate, or combinations thereof.
24. The method of claim 17, wherein the alkali metal silicate
binder comprises a pigment.
25. The method of claim 17, wherein each of the absolute values of
the difference in the L*, a*, b* numbers between the coated article
and the base article is less than about 2.
26. A method of making a coated roofing granule, comprising:
providing a roofing granule having an external surface, providing a
composition comprising a dispersion of photocatalysts having a mean
cluster size of less than about 300 nm and an alkali metal silicate
binder, depositing the composition onto the roofing granule, and
heating the deposited roofing granule to form a coating thereon,
wherein each of the absolute values of the difference in the L*,
a*, b* numbers between the coated granule and the base granule is
less than about 2.
Description
FIELD OF INVENTION
[0001] The present invention relates to a coating composition and a
coated article having a photocatalytic coating formed therefrom,
particularly with application to building materials, such as, for
example, roofing granules.
BACKGROUND
[0002] Discoloration of construction surfaces due to algae growth
or other agents has been a problem for the construction industry
for many years. Discoloration has been attributed to the presence
of blue-green algae and other airborne contaminants, such as soot
and grease.
[0003] One approach to combating this problem is to coat the
construction surfaces with a composition that contains
photocatalysts and a binder, typically a silicate binder. When
exposed to sunlight, the photocatalysts may photo-oxidize the
organic materials that cause the discoloration.
[0004] Photocatalytic titanium dioxide (TiO.sub.2) particles can be
used, for example, in roofing granules, to provide photocatalytic
activity. Suitable TiO.sub.2 particles are often very small, having
a mean particle size in the range of about 1 nm to about 1000 nm.
Such particles have strong surface interactions due to their high
surface-to-volume ratios and without any treatment they tend to
aggregate to form larger clusters. As a consequence, a relatively
high amount of TiO.sub.2 particles need to be used to achieve an
acceptable level of photoactivity. This usually makes the coated
granules pastel in color and thus lose aesthetic appeals.
SUMMARY
[0005] The present invention is directed to a coating composition
and a coated article resulting from the application of the coating
composition.
[0006] The coating composition of the present invention generally
includes a dispersion of photocatalysts having a mean cluster size
of less than about 300 nm and an alkali metal silicate binder. The
dispersion can be made by mixing the photocatalysts, a dispersant
and a solvent. Preferably, the photocatalysts are transition metal
oxides. Particularly preferred photocatalysts include crystalline
anatase TiO.sub.2, crystalline rutile TiO.sub.2, crystalline ZnO
and combinations thereof. The coating composition has a solid
weight percentage of photocatalysts in the range of about 0.1% to
about 90%. Preferred weight percentage is in the range of about 30%
to about 80%. Examples of suitable dispersants include inorganic
acids, inorganic bases, organic acids, organic bases, anhydrous or
hydrated organic acid salts and combinations thereof. Suitable
solvents can be any solvents that dissolve the dispersant used.
Examples of suitable alkali metal silicate binders include lithium
silicate, sodium silicate, potassium silicate, and combinations
thereof.
[0007] Applying the coating composition onto a base article,
followed by heating to elevated temperatures in a rotary kiln, oven
or other suitable apparatus, produces a photocatalytic coating with
improved transparency that exhibits desirable photoactivity.
Preferred articles include building materials susceptible to
discoloration due to algae growth or other agents, such as airborne
particulates of dust, dirt, soot, pollen or the like. One
particularly preferred article is roofing granules.
DETAILED DESCRIPTION
[0008] The present invention is directed to a coating composition
comprising a dispersion of photocatalysts having a mean cluster
size of less than about 300 nm and an alkali metal silicate binder
and a coated article having a photocatalytic coating with improved
transparency. In the present invention, the transparency of a
photocatalytic coating is characterized by measuring the difference
in the L*, a*, b* numbers between the coated article and the base
article, and preferably each of the absolute values of the
difference measured is less than about 2. The L*, a*, b* numbers
indicate color scales in light-dark, red-green, and yellow-blue,
respectively, and all three numbers are needed to describe the
color of an object. For two different objects, the difference in
their L*, a*, b* numbers represents the difference in their
colors.
[0009] The photocatalytic coating is formed by applying the coating
composition onto the base article, followed by heating to elevated
temperatures of at least about 170.degree. C. and up to about
650.degree. C., with a preferred temperature of about 200.degree.
C. to about 450.degree. C. The coating protects the base article
against discoloration caused by algae growth or other agents. For
purposes of the present invention, the coating may have multiple
layers.
[0010] Base articles suitable for use with the present invention
can be any ceramic, metallic, or polymeric materials or composites
thereof that are capable of withstanding temperatures of at least
about 170.degree. C. Preferred articles include building materials
that are susceptible to discoloration due to algae infestation or
other agents, such as airborne particulates of dust, dirt, soot,
pollen or the like. Examples include roofing materials, concrete
and cement based materials, plasters, asphalts, ceramics, stucco,
grout, plastics, metals or coated metals, glass, or combinations
thereof. Additional examples include pool surfaces, wall coverings,
siding materials, flooring, filtration systems, cooling towers,
buoys, seawalls, retaining walls, boat hulls, docks, and canals.
One particularly preferred article is roofing granules, such as
those formed from igneous rock, argillite, greenstone, granite,
trap rock, silica sand, slate, nepheline syenite, greystone,
crushed quartz, slag, or the like, and having a particle size in
the range from about 300 .mu.m to about 5000 .mu.m in diameter.
Roofing granules are often partially embedded onto a base roofing
material, such as, for example, asphalt-impregnated shingles, to
shield the base material from solar and environmental degradation.
Another particularly preferred article is tiles, such as those
formed from ceramics, stones, porcelains, metals, polymers, or
composites thereof. Tiles are often used for covering roofs,
ceilings, floors, and walls, or other objects such as tabletops to
provide wear, weather and/or fire resistances.
[0011] The coating composition of the present invention comprises a
dispersion of photocatalysts. Upon activation or exposure to
sunlight, the photocatalysts are thought to establish both
oxidation and reduction sites. These sites are thought to produce
highly reactive species such as hydroxyl radicals that are capable
of preventing or inhibiting the growth of algae or other biota on
the coated article, especially in the presence of water.
[0012] The dispersion can be made, for example, by mixing the
photocatalysts, a dispersant and a solvent. Many photocatalysts
conventionally recognized by those skilled in the art are suitable
for use with the present invention. Preferred photocatalysts
include transition metal photocatalysts. Examples of suitable
transition metal photocatalysts include TiO.sub.2, ZnO, WO.sub.3,
SnO.sub.2, CaTiO.sub.3, Fe.sub.2O.sub.3, MoO.sub.3,
Nb.sub.2O.sub.5, Ti.sub.xZr.sub.(1-x)O.sub.2, SiC, SrTiO.sub.3,
CdS, GaP, InP, GaAs, BaTiO.sub.3, KNbO.sub.3, Ta.sub.2O.sub.5,
Bi.sub.2O.sub.3, NiO, Cu.sub.2O, SiO.sub.2, MoS.sub.2, InPb,
RuO.sub.2, CeO.sub.2, Ti(OH).sub.4, and combinations thereof.
Particularly preferred photocatalysts include crystalline anatase
TiO.sub.2, crystalline rutile TiO.sub.2, crystalline ZnO and
combinations thereof. To improve spectral efficiency, the
photocatalysts may be doped with a nonmetallic element, such as C,
N, S, F, or with a metal or metal oxide, such as Pt, Pd, Au, Ag,
Os, Rh, RuO.sub.2, Nb, Cu, Sn, Ni, Fe, or combinations thereof.
[0013] Suitable dispersants may be inorganic acids, inorganic
bases, organic acids, organic bases, anhydrous or hydrated organic
acid salts and combinations thereof. Examples of inorganic acids
include binary acids such as hydrochloric acid; and oxoacids such
as nitric acid, sulfuric acid, phosphoric acid, perchloric acid and
carbonic acid. Examples of inorganic bases include ammonia and
hydroxides of lithium, sodium, potassium, rubidium, and cesium.
Examples of organic acids include monocarboxylic acids such as
formic acid, acetic acid and propionic acid; dicarboxylic acids
such as oxalic acid, glutaric acid, succinic acid, malonic acid,
maleic acid and adipic acid; tricarboxylic acids such as citric
acid; and amino acids such as glycine. Examples of organic bases
include urea, purine and pyrimidine. Examples of organic acid salts
include ammonium carboxylates such as ammonium acetate, ammonium
oxalate and ammonium hydrogen oxalate, ammonium citrate and
ammonium hydrogen citrate; and carboxylic acid salts such as
oxalates and hydrogen oxalates of lithium, sodium and potassium,
and oxalates of magnesium, yttrium, titanium, zirconium, vanadium,
chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel,
ruthenium, rhodium, palladium, osmium, iridium, platinum, copper,
silver, gold, zinc, gallium, indium, germanium, tin, lanthanum, and
cerium.
[0014] Suitable solvents can be any solvents that dissolve the
dispersant used. Examples include water-based solvents such as
water and hydrogen peroxide water; alcohols such as ethanol,
methanol, 2-propanol and butanol; ketones such as acetone and
2-butanone; paraffin compound solvents; and aromatic compound
solvents.
[0015] The photocatalysts in the dispersion may aggregate to form
clusters owing to their surface interactions. The clusters formed
have a mean size of less than about 300 nm. Mean cluster size can
be determined by light scattering. Mean cluster size is different
from mean particle size. Mean particle size characterizes
individual particles of photocatalysts and is often measured using
electron microscopy. Examples of commercially available TiO.sub.2
dispersions that have a mean cluster size of less than about 300 nm
include the STS-21 dispersion (available from Ishihara Sangyo
Kaisha, Japan) and the W2730X dispersion (available from Degussa
AG, Germany). The use of such dispersion in the present invention
produces photocatalytic coatings with improved transparency that
exhibit desirable photoactivity.
[0016] The coating composition has a solid weight percentage of
photocatalysts in the range of about 0.1% to about 90%. Preferred
weight percentage is in the range of about 30% to about 80%.
[0017] Examples of suitable alkali metal silicate binders include
lithium silicate, sodium silicate, potassium silicate, and
combinations thereof. Alkali metal silicate is generally denoted as
M.sub.2O:SiO.sub.2, where M is lithium, sodium, or potassium. The
weight ratio of SiO.sub.2 to M.sub.2O may range from about 1.4:1 to
about 3.75:1. A preferred weight ratio is in the range of about
2.75:1 to about 3.22:1.
[0018] A pigment, or a combination of pigments, may be included in
the coating composition to achieve a desired color. Suitable
pigments include conventional pigments, such as carbon black,
titanium oxide, chromium oxide, yellow iron oxide, phthalocyanine
green and blue, ultramarine blue, red iron oxide, metal ferrites,
and combinations thereof.
[0019] The durability of the photocatalytic coating of the present
invention can be enhanced by adding an alkoxysilane (as disclosed
in 3M Patent Application No. 62043US002, filed on Dec. 22, 2006,
the entirety of which is incorporated herein by reference) and/or
by adding a boric acid, borate, or combination thereof (as
disclosed in 3M Patent Application No. 62617US002, filed on Dec.
22, 2006, the entirety of which is incorporated herein by
reference) to the coating composition.
EXAMPLES
[0020] The operation of the present invention will be further
described with regard to the following detailed examples. These
examples are offered to further illustrate the various specific and
preferred embodiments and techniques. It should be understood,
however, that many variations and modifications may be made while
remaining within the scope of the present invention.
[0021] Measurement of Mean Cluster Size
[0022] The mean cluster size of the STS-21 dispersion of TiO.sub.2
was measured using a Nanosizer (Nano-ZS series, available from
Malvern Instruments, United Kingdom). The procedure for measuring
the mean cluster size is as follows. About 0.02 g of the dispersion
was diluted with 30 g of deionized water. The diluted dispersion
was well shaken and then about 3 ml of the diluted dispersion was
transferred into a 10-ml plastic syringe that is fitted with a
4.5-.mu.m filter. The filtered dispersion was then used to measure
the mean cluster size. This process was repeated twice, and the
average of the three measurements was reported.
[0023] Measurement of L*, a *, b* Numbers
[0024] The granules were placed into a round sample holder with a
diameter of 3 inches. The granules were then pressed so that they
were flat and even with the edges of the holder. The holder was
placed into a LabScan XE spectrophotometer (HunterLab, Reston,
Va.), and a scan was taken. The holder was then emptied and
reloaded, and another scan was taken. The two scans were averaged
to produce the L*, a*, b* numbers of the granules.
[0025] Photocatalytic Activity Test
[0026] The granules were sieved through a -16/+20 mesh, washed 5
times by deionized water and then dried at 240.degree. F.
(.about.116.degree. C.) for about 20 minutes. 40 g of the dried
granules was placed into a 500 mL crystallization dish. 500 g of
4.times.10.sup.-4 M aqueous disodium terephthalate solution was
then added to the dish. The mixture was stirred using a magnetic
bar placed in a submerged small Petri dish and driven by a magnetic
stirrer underneath the crystallization dish. The mixture was
exposed to UV light produced by an array of 4, equally spaced, 4-ft
(1.2-m) long black light bulbs (Sylvania 350 BL 40W F40/350BL) that
were powered by two specially designed ballasts (Action Labs,
Woodville, Wis.). The height of the bulbs was adjusted to provide
about 2.3 mW/cm.sup.2 UV flux measured using a VWR Model 21800-016
UV Light Meter (VWR International, West Chester, Pa.) equipped with
a UVA Model 365 Radiometer (Solar Light Company, Glenside, Pa.)
having a wavelength band of 320-390 nm.
[0027] During irradiation, about 3 mL of the mixture was removed
with a pipet at about 5-minute intervals and transferred to a
disposable 4-window polymethylmethacrylate or quartz cuvette. The
mixture in the cuvette was then placed into a Fluoromax-3
spectrofluorimeter (Jobin Yvon, Edison, N.J.). The fluorescence
intensity measured at excitation wavelength of 314 nm and emission
wavelength of 424 nm was plotted against the irradiation time. The
slope of the linear portion (the initial 3-5 data points) of the
curve was indicative of the photocatalytic activity of the mixture.
A comparison of this slope with that for the aqueous disodium
terephthalate solution provided the relative photoactivity of the
granules as reported. In general, the larger the reported value,
the greater the photoactivity of the granules.
Working Examples 1-3
[0028] Blank red granules were prepared as follows. 43.02 g of
sodium silicate (Sodium Silicate PD, available from PQ Corporation,
Valley Forge, Pa.), 16.00 g of deionized water, 6.57 g of Red Iron
Oxide M201Y (available from Revelli Chemicals, Greenwich, Conn.),
4.13 g of Red Iron Oxide RO-5097 (available from Harcros Chemicals,
Kansas City, Kans.), and 10.95 g of Dover Clay (available from
Grace Davison, Columbia, Mass.) were added to a 250 mL vessel and
well mixed. The resulting mixture was then slowly poured onto 1000
g of stirring Grade #11 uncoated granules (available from 3M
Company, St. Paul, Minn.), which had been pre-heated to 210.degree.
F. (.about.99.degree. C.) for one hour. While pouring, the granules
were mixed to ensure an even coating. The granules were further
stirred for about 2 minutes and then heated with a heat gun until
they appeared to be dry and loose. The dried granules were then
fired in a rotary kiln (natural gas/oxygen flame) to 800.degree. F.
(.about.427.degree. C.), and removed and allowed to cool to room
temperature.
[0029] The red granules with photocatalytic coating for Working
Example 1 were prepared as follows. 0.34 g of potassium silicate
(Kasil 1, available from PQ Corporation), 0.51 g of aqueous
dispersion of TiO.sub.2 (STS-21, available from Ishihara Sangyo
Kaisha, Japan), and 40.79 g of deionized water were added to a 250
mL vessel and well mixed. The resulting mixture was then slowly
poured onto stirring blank red granules prepared as described
above, which had been pre-heated to 210.degree. F. for one hour.
While pouring, the granules were mixed to ensure an even coating.
The granules were further stirred for about 2 minutes and then
heated with a heat gun until they appeared to be dry and loose. The
dried granules were then fired in a rotary kiln (natural gas/oxygen
flame) to 800.degree. F., and removed and allowed to cool to room
temperature. The red granules with photocatalytic coating for
Working Examples 2 & 3 were prepared using the same procedure
except that different coating compositions were used. The
compositions of the photocatalytic coatings for Working Examples
1-3 are listed in Table 1. The mean cluster size of the STS-21
dispersion was measured as about 220 nm according to the testing
procedure described above.
[0030] The L*, a*, b* numbers and photocatalytic activity for the
red granules with photocatalytic coating were measured according to
the testing procedures described above, and reported in Table 1.
For comparison, the L*, a*, b* numbers and photocatalytic activity
for the blank red granules were also measured and reported in Table
1. The results show that the use of a TiO.sub.2 dispersion having a
relatively small mean cluster size produces photocatalytic coatings
that have minimal impact on color and exhibit desirable
photoactivity.
TABLE-US-00001 TABLE 1 Compositions of Photocatalytic Coatings, L*,
a*, b* Numbers and Photocatalytic Activity for Working Examples
1-3. Kasil 1 STS-21 DI H.sub.2O Firing Temp Example (g) (g) (g)
(.degree. F.) L* a* b* Photoactivity 1 0.34 0.51 40.79 800 31.03
21.68 17.71 1.7 .times. 10.sup.4 2 0.36 1.03 40.33 800 31.05 22.18
17.46 7.1 .times. 10.sup.4 3 0.70 0.99 40.73 800 31.11 21.62 17.48
3.7 .times. 10.sup.4 Blank Red Granules 31.14 22.51 17.88 1.4
.times. 10.sup.3
Working Examples 4-6
[0031] Blank olive granules were prepared using the same procedure
as that for preparing the blank red granules in Working Examples
1-3 except that a different coating composition was used.
Specifically, the coating composition was made by adding 35.37 g of
Sodium Silicate PD, 13.67 g of deionized water, 6.10 g of Mapico
Tan Iron Oxide 10A (available from Rockwood Pigments, Beltsville,
Md.), 0.53 g of Carbon Black M-8452 (available from Rockwood
Pigments), 2.64 g of Burnt Umber L1361 (available from Rockwood
Pigments), 1.70 g of Chromium Oxide 112 (available from Elementis
Chromium, Corpus Christi, Tex.), and 8.13 g of Dover Clay
(available from Grace Davison, Columbia, Mass.) to a 250 mL vessel,
followed by well mixing.
[0032] The olive granules with photocatalytic coating for Working
Examples 4-6 were prepared using the same procedure as that for
preparing the red granules with photocatalytic coating for Working
Example 1 except that different coating compositions were used and
the granules used were blank olive granules instead of blank red
granules. The compositions of the photocatalytic coatings for
Working Examples 4-6 are listed in Table 2.
[0033] The L*, a*, b* numbers and photocatalytic activity for the
olive granules with photocatalytic coating were measured according
to the testing procedures described above, and reported in Table 2.
For comparison, the L*, a*, b* numbers and photocatalytic activity
for the blank olive granules were also measured and reported in
Table 2. The results also show that the use of a TiO.sub.2
dispersion having a relatively small mean cluster size produces
photocatalytic coatings that have minimal impact on color and
exhibit desirable photoactivity.
TABLE-US-00002 TABLE 2 Compositions of Photocatalytic Coatings, L*,
a*, b* Numbers and Photocatalytic Activity for Working Examples
4-6. Kasil 1 STS-21 DI H.sub.2O Firing Temp Example (g) (g) (g)
(.degree. F.) L* a* b* Photoactivity 4 0.36 0.51 40.42 800 28.39
1.63 8.51 8.3 .times. 10.sup.3 5 0.37 1.00 40.35 800 27.95 1.92
7.84 1.1 .times. 10.sup.5 6 0.71 1.02 40.02 800 28.13 1.97 8.09 6.7
.times. 10.sup.4 Blank Olive Granules 28.23 2.03 9.71 2.4 .times.
10.sup.3
[0034] The tests and test results described above are intended
solely to be illustrative, rather than predictive, and variations
in the testing procedure can be expected to yield different
results. The present invention has now been described with
reference to several embodiments thereof. The foregoing detailed
description and examples have been given for clarity of
understanding only. No unnecessary limitations are to be understood
therefrom. All patents and patent applications cited herein are
hereby incorporated by reference. It will be apparent to those
skilled in the art that many changes can be made in the embodiments
described without departing from the scope of the invention. Thus,
the scope of the present invention should not be limited to the
exact details and structures described herein, but rather by the
structures described by the language of the claims, and the
equivalents of those structures.
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